Fabric conditioning compositions are commonly used to deposit a fabric softening compound onto fabric. Typically, such compositions contain a cationic fabric softening agent dispersed in water. Compositions containing softening agent below 5% by weight are considered ultra dilute. Compositions having around 5% softening agent are considered dilute, whilst softening agent levels in the range 5-10% by weight are termed semi dilute. Levels of softening agent from 10% to 50% by weight are considered concentrated. Dilute, ultra dilute and semi-dilute fabric conditioning compositions can suffer from problems of low viscosity. Consumers associate a high viscosity with good performance and product quality. A viscosity of at least 35 mPa·s at a shear rate of 106 s−1 measured at ambient temperature is typically desirable.
The viscosity of ultra dilute, dilute and semi-dilute fabric conditioning compositions can be increased by including polymeric viscosity control agents, for example starches and cellulose ethers. However, these conventional viscosity control agents are expensive materials. They have to be included at levels in the range 0.05-1% by weight, which increases the costs of fabric conditioning compositions which include them. Furthermore, conventional polymeric viscosity control agents tend to show a drop in viscosity on storage. Further, they typically require a separate gelatinisation stage, in which they are mixed with water, which can increase the complexity and expense of the manufacturing process.
The present invention sets out to provide ultra dilute, dilute and semi dilute fabric conditioning compositions and processes for preparing them which achieve desirable viscosities without incorporating large quantities of expensive components.
The present inventors have discovered that a fatty acid partial ester of a polyhydric alcohol can act as a viscosity modifier, even when included at very low levels (for example below 0.2% by weight), if the fabric conditioning composition is manufactured under certain conditions. In particular, it is necessary to expose the fabric conditioning composition to shear at a temperature below the phase transition temperature of the fabric conditioning composition.
Fatty acid partial esters of polyhydric alcohols are themselves well known in fabric conditioning compositions. In particular, they are typically included as fabric softening components in their own right, for example as disclosed in EP-A-0000406 (Procter & Gamble); GB 1550205 (Procter & Gamble) and WO 97/16516 (Procter & Gamble).
WO 97/08285 (Colgate/Palmolive Company) discloses the use of fatty acid esters of mono or polyhydric alcohols as emulsion or dispersion stabilisers in fabric softening compositions containing 3-40% by weight of a fabric softener combination comprising an amido tertiary amine and an ester quat material. The weight ratio of fabric softener combination to fatty acid ester of mono or polyhydric alcohol is in the range 40:1 to about 5:1 and the level of fatty acid ester of mono- or polyhydric alcohol in the composition is in the range 0.2-2% by weight. There is no mention that lower levels of fatty acid ester of mono- or polyhydric alcohol can lead to unexpected increases in viscosity.
GB 2204608 (Kao Corporation) discloses liquid softener compositions comprising a quaternary ammonium salt, a polyamide and an ester derived from a fatty acid having 10-24 carbon atoms and glycerol, the weight ratio of quaternary ammonium salt to ester being in the range 0.1:1 to 3:1. There is, however, no mention of including a specific processing step in which the mixture is exposed to shear below the phase transition temperature of the system. There is no disclosure that the compositions can accordingly have unexpectedly high viscosities.
JP 63-295764 (Kao Corporation) discloses soft finishing agents containing (a) a cationic textile softening substance, (b) a straight chain fatty acid and (c) an esterified product of fatty acid and glycerol. The molar ratio of (b):(a) is 0.001 to 0.2, the weight ratio of (b):(a) is 0.01 to 3 and the total amount of (a), (b) and (c) is 3 to 20 wt %. There is no disclosure that stable thickening of compositions can be achieved through shear below the phase transition temperature of (a).
DE-A1-4400927 (Henkel) discloses aqueous solutions of quaternised fatty acid triethanolamine ester salts thickened by adding 0.01 to 0.1 wt % of esters of fatty acids with commercial oligoglycerol mixtures. There is no mention of mono-glycerol based viscosity modifies and no disclosure of a shearing step below the phase transition temperature of the system.
EP-A2-0060003 discloses concentrated textile treatment compositions comprising 12 to 25% of a water insoluble quaternary ammonium compound, a water soluble alkoxylated ammonium surfactant and a fatty acid ester of a polyhydric alcohol. There is no disclosure or teaching in relation to dilute compositions. Also page 7 of this document discloses a method of preparing the composition whereby the mixing clearly takes place above the phase transition temperature.
GB 1599171 (Procter & Gamble) discloses an aqueous textile treatment composition comprising a water insoluble cationic fabric softener, a water insoluble nonionic fabric softener and from 0.1 to 10 wt % of an aromatic carboxylic acid. The nonionic fabric softener is present in an amount from 0.5 to 12 wt %. There is no disclosure of the specific processing conditions of the present invention.